<?php

// +----------------------------------------------------------------------

// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]

// +----------------------------------------------------------------------

// | Copyright (c) 2009 http://thinkphp.cn All rights reserved.

// +----------------------------------------------------------------------

// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )

// +----------------------------------------------------------------------

// | Author: liu21st <liu21st@gmail.com>

// +----------------------------------------------------------------------

namespace Think\Crypt\Driver;

/**

 * Crypt 加密实现类

 * @category   ORG

 * @package  ORG

 * @subpackage  Crypt

 * @author    liu21st <liu21st@gmail.com>

 */

class Crypt {



    /**

     * 加密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @param integer $expire 有效期（秒）     

     * @return string

     */

    public static function encrypt($str,$key,$expire=0){

        $expire = sprintf('%010d', $expire ? $expire + time():0);

        $r = md5($key);

        $c=0;

        $v = "";

        $str    =   $expire.$str;

		$len = strlen($str);

		$l = strlen($r);

        for ($i=0;$i<$len;$i++){

         if ($c== $l) $c=0;

         $v.= substr($r,$c,1) .

             (substr($str,$i,1) ^ substr($r,$c,1));

         $c++;

        }

        return self::ed($v,$key);

    }



    /**

     * 解密字符串

     * @param string $str 字符串

     * @param string $key 加密key

     * @return string

     */

    public static function decrypt($str,$key) {

        $str = self::ed($str,$key);

        $v = "";

		$len = strlen($str);

        for ($i=0;$i<$len;$i++){

         $md5 = substr($str,$i,1);

         $i++;

         $v.= (substr($str,$i,1) ^ $md5);

        }

        $data   =    $v;

        $expire = substr($data,0,10);

        if($expire > 0 && $expire < time()) {

            return '';

        }

        $data   = substr($data,10);

        return $data;

    }





   function ed($str,$key) {

      $r = md5($key);

      $c=0;

      $v = "";

	  $len = strlen($str);

	  $l = strlen($r);

      for ($i=0;$i<$len;$i++) {

         if ($c==$l) $c=0;

         $v.= substr($str,$i,1) ^ substr($r,$c,1);

         $c++;

      }

      return $v;

   }

}